1. Technical Field of the Invention
The present invention relates to solar battery modules, in particular, a solar battery module suitably used when solar battery cells are efficiently placed thereon as much as possible.
2. Disclosure of Related Art
Against a backdrop of problems such as exhaustion of oil resources and global warming, recently, development and popularization of a clean energy source employing no oil resources are mentioned as a global challenge. A photovoltaic power generating system uses inexhaustible photovoltaic energy without emission of CO2 or the like and, therefore, receives attention as a solution for such problems.
In order to protect a solar battery cell which is a power generating source from external damage and improve handleability, the photovoltaic power generating system typically uses a solar battery module including several tens of solar battery cells arranged on a plane. Herein, the solar battery module is typically formed into a rectangular shape having a side of about one meter in order to efficiently arrange solar battery cells in a certain area and to improve handleability upon transfer or installation thereof.
On the other hand, an ingot (single crystal silicon) used as a material for a substrate of a solar battery cell is formed into a cylindrical shape because of its manufacturing method. Therefore, when a substrate of a solar battery cell is obtained by slicing the ingot, the solar battery cell is inevitably formed into a circular shape. Herein, even when solar battery cells are efficiently placed on a solar battery module as much as possible, a large clearance is created between adjoining solar battery cells as illustrated in (a-1) and (a-2) of FIG. 11, for example. Consequently, there arises a problem that solar battery cells 10 to be placed on a solar battery module 20 are small in number.
In order to solve this problem, a solar battery cell 10 is formed into a square shape as illustrated in (b-1) and (b-2) of FIG. 11. Thus, solar battery cells 10 to be placed on a solar battery module 20 can be increased in number. However, there arises another problem that wasted portions (hatched portions in (b-2) of FIG. 11) from which a substrate 31 can not be obtained become large in an ingot 30, that is, the ingot 30 can not be used efficiently.
Alternatively, a solar battery cell 10 is formed into a hexagonal shape as illustrated in (c-1) and (c-2) of FIG. 11. Thus, solar battery cells 10 to be placed on a solar battery module 20 can be increased in number as compared with the case that the solar battery cell 10 is formed into a circular shape. Further, an ingot 30 can be used more efficiently as compared with the case that the solar battery cell 10 is formed into a square shape. Also in this case, however, a clearance where a solar battery cell 10 can not be placed is created in the solar battery module 20, and wasted portions from which a substrate 31 can not be obtained still remain in the ingot 30.
In order to solve these problems, JP2001-094127A discloses a solar battery module by which solar battery cells 10 to be placed thereon can be increased in number and an ingot 30 an be used efficiently. According to this prior invention, a substrate 31 is cut out from the ingot 30 so as to have a hexagonal shape which is larger than a hexagonal shape inscribed in an outer periphery of the ingot 30 and is smaller than a hexagonal shape inscribed by the outer periphery of the ingot 30 (hereinafter, a shape cut out in this manner will be referred to as an “almost hexagonal shape”), as illustrated in FIG. 12B. Thus, wasted portions from which a substrate 31 can not be obtained can be reduced in the ingot 30, that is, the ingot 30 can be used efficiently.
In this prior invention, further, a solar battery cell 10 including such a substrate 31 cut out as described above is divided into two or four at a line P-P′ and/or a line Q-Q′ in FIG. 12B. Then, the divided solar battery cells 10 are arranged as illustrated in FIG. 12A or 12C. Thus, a clearance where a solar battery cell 10 can not be arranged is reduced in a solar battery module 20, that is, solar battery cells 10 to be placed on the solar battery module 20 can be increased in number.
Alternatively, JP09-148601A (1997) discloses the following configuration. That is, a solar battery cell having a hexagonal shape or an almost hexagonal shape is divided into two at a straight line connecting opposed apexes or a straight line connecting two division points on opposed sides. Then, the divided solar battery cells are placed on a solar battery module. FIG. 13A illustrates the configuration of the solar battery module according to this prior invention, and FIG. 13B is a sectional view taken along a line R-R′ in FIG. 13A.
According to this prior invention, solar battery cells 10 are placed on the solar battery module 20 such that identical polarities thereof are directed in a single direction. Then, an interconnector 21 connects between a front surface or a back surface of one of adjoining solar battery cells 10 and a back surface or a front surface of the other solar battery cell 10; thus, the solar battery cells 10 are electrically connected to each other.
With the configuration in JP09-148601A, however, oblique sides of divided cells oppose each other, and an interconnector is routed from a front surface of one cell to a back surface of another cell at a portion where the oblique sides of the divided cells oppose each other. Consequently, there arises a problem that a clearance at the portion becomes relatively large, so that solar battery cells to be placed on a solar battery module are reduced in number. In addition, the interconnector routed at the portion readily causes chipping or cracking of the divided cells, so that there may arise a problem that a divided cell is damaged. Further, in a case that a plurality of interconnectors are used for connection between adjoining divided cells, the interconnectors are disadvantageously bent at an oblique side of the divided cell. Consequently, a position at which an interconnector is bent in an oblique side differs for each interconnector, so that there arises a problem that connection work using an interconnector becomes complicated.
Moreover, JP2001-094127A discloses no interconnection between divided cells using an interconnector.